The preferred appearance of most fruit varieties is a clear, smooth surface. Fruit with imperfections or blemishes on the fruit surfaces known as russetting are generally considered inferior by consumers. Accordingly, such fruit brings a considerably lower price to producers. Additionally, russetted fruits also are not as amenable to long-term storage as fruit without such imperfections. Thus, fruit russetting is one of the major horiticultural problems associated with the production of various fruits.
Because of the importance of fruit russetting to crops such as pears and apples, there is a considerable body of world-wide literature on this phenomenon. Most of the references are either etiological or are rather anecdotal. For example, considerable attention has been given to the development of fruits, particularly the epidermal cell layers, during the growth process. There is a general understanding that cracks in the cuticle layer of the fruit surface and/or the death of individual epidermal cells by different causes stimulate the production of cells containing considerable amount of cutin and cork. Such dead cells lead to the rough, browned appearance that is typical of russetting.
One major school of thought has been that russetting is induced in the earliest stages of fruit development (from 1-4 weeks after the flowers fall from the trees). During this time the surface area of the fruit is expanding most rapidly (from a relative view point). The stretching of the epidermal cells to cause breaks in the cuticle and/or death in the cells has been considered one cause of fruit russetting. Additionally, fruit russetting has been associated with various environmental and chemical causes, such as cool, moist weather and orientation of the growing fruit to the environment. Fruit russetting has been examined almost exclusively by plant physiologists, botanists, and horticulturists from the standpoint of the response of the developing fruit to its physical and environmental surroundings.
Efforts to reduce fruit russetting have generally been ineffective. Recent experimental applications of gibberellic acid have shown some promise but have been sporadic in their results and have caused undesirable changes in the fruit morphology and/or other detrimental effects on plant growth. Accordingly, there remains considerable need for improved techniques for reducing fruit russetting.